<!DOCTYPE html>
<html lang="zh_CN">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        /* * 一般做页面样式的重置操作 */

        html, body, div, span, applet, object, iframe,
        h1, h2, h3, h4, h5, h6, p, blockquote, pre,
        a, abbr, acronym, address, big, cite, code,
        del, dfn, em, img, ins, kbd, q, s, samp,
        small, strike, strong, sub, sup, tt, var,
        b, u, i, center,
        dl, dt, dd, ol, ul, li,
        fieldset, form, label, legend,
        table, caption, tbody, tfoot, thead, tr, th, td,
        article, aside, canvas, details, embed,
        figure, figcaption, footer, header, hgroup,
        menu, nav, output, ruby, section, summary,
        time, mark, audio, video {
            margin: 0;
            padding: 0;
            border: 0;
            font-size: 100%;
            font: inherit;
            vertical-align: baseline;
        }

        /* HTML5 display-role reset for older browsers */
        article, aside, details, figcaption, figure,
        footer, header, hgroup, menu, nav, section {
            display: block;
        }

        body {
            line-height: 1;
        }

        ol, ul {
            list-style: none;
        }

        blockquote, q {
            quotes: none;
        }

        blockquote:before, blockquote:after,
        q:before, q:after {
            content: '';
            content: none;
        }

        table {
            border-collapse: collapse;
            border-spacing: 0;
        }

        .div1 {
            border: 1px solid #000;
        }

        /*，是并集，*/
        /*p.p1交集*/
        .div1 > a, p.p1 {
            color: red;
        }


    </style>
</head>
<body>
<div class="div1">
    <p>段落1</p>
    <p class="p1">段落1</p>
    <p>段落1</p>
    <div>我是盒子</div>
    <h1>我的标题</h1>
    <a href="https://www.baidu.com/">百度1</a>
    <div class="div2">
        <a href="https://www.baidu.com/">百度2</a>
    </div>
</div>
<a href="https://www.baidu.com/">百度3</a>
</body>
<script type="text/javascript">

</script>

</html>
